Apparatus for selective electroplating of strips

ABSTRACT

Apparatus for continuously electroplating pre-selected portions on the surface of continuously-moving metal strips wherein the strips are carried through an agitated bath of electrolyte while biased between sealing webs which have apertures allowing electrolyte to contact only the aforesaid pre-selected surface portions.

July 17, 1973 N KOSOWSKY ET AL 3,746,630

APPARATUS FOR SELECTIVE ELECTROPLATING OF STRIPS 1 LMIEECQ O v a fi Mmmz mmj m SIX a L 3 w m f m mm o 0 0p INVENTORS Leo N. Kosowsky Curtis N.Lovejoy John G.'Cunniff & m d m. m

ATTORNEYS 5 Nn v IJQQIJ M )1 mm 8 W NN N. w. w. 2 w r f u M w. W o 3 a 8ON 7. NM ON A c n an 3 3 8 m m M on L g L L L Q M .3 F. r a m h. w S

July 17, 4 L KQSOWSKY ET Al 3,746,630

v APPARATUS FOR SELECTIVE I'ZLIJCTROIIIA'IINU OI STRIPS Filed Dec. 8,1970 2 Sheets-Sheet '2 69 i 5- 4-fi 2 44 @44 I 43 /M 43 43 a 6' 5 a 426/ Fig.2

Leo

A Curtis N. Lovejoy 66 John G. Cunniff Fi 7 BY Robert T. Groom 6850/11 6777cA awa ATTORNEYS United States Patent 3,746,630 APPARATUS FORSELECTIVE ELECTROPLATING on STRIPS US. Cl. 204-406 Claims ABSTRACT OFTHE DISCLOSURE Apparatus for continuously electroplating pre-selectedportions on the surface of continuously-moving metal strips wherein thestrips are carried through an agitated bath of electrolyte while biasedbetween sealing webs which have apertures allowing electrolyte tocontact only I the aforesaid pre-selected surface portions.

BACKGROUND OF THE INVENTION (1) Field of the invention This inventionrelates to apparatus and process for continuously and uniformlyelectroplating a plurality of preselected isolated areas of an elongatestrip while maintaining the rest of the substrate out of contact withthe electroplating bath.

(2) The prior art In many electroplating operations, e.g., operationswherein microcircuits are electroplated with gold, there is a need tominimize the amount of expensive metal utilized by closely restrictingits deposition to only those surface areas where its presence isessential. It is desirable, however, that such selective deposition ofthe metal be achieved without resorting to procedures which greatlyrestrict the production rate of an electroplating facility or toprocedures which greatly increase the handling costs of the items beingelectroplated.

It has been known to use organic coatings to mask those areas ofmetallic substrates on which electroplating is not required and therebyavoid those areas being electroplated. After the electroplating step isfinished, the masking material is removed, leaving the discreteelectroplated zones. Such a process requires expensive coating andstripping steps. These steps add to the cost of the electroplatingoperation and also increase the probability that some of the costly workproduct will have to be scrapped because of damage incurred during themanufacturing operations.

Previous suggestions have been made for accomplishing the electroplatingof small selected areas, but these suggestions have been limited tosmall-scale, repair-type operations wherein the rigorous requirements ofhigh-rate or continuous manufacture need not be considered. All of theseprior suggestions are believed to be batch-type processes. For example,Ehrhart, in U.S. Pat. No. 3,071,521, discloses a single grommet-sealedchamber for use in repairing printed-circuits. Swanson, in US. Pat. No.2,698,832, discloses a somewhat similar device utilizing a reservoir foran electroplating solution adapted to empty, by gravity flow, into areceptacle for receiving the solution. Neither of these inventions hassuggested a way whereby a large number of discrete areas can be carriedout continuously at optimum current densities. Indeed, neither inventor,in solving his own particular problem, has been faced with problems ascomplex as those involved in the electroplating of a plurality ofisolated areas on a continuously-advancing strip of substrate.

Ramirez et al., in US. Pat. No. 2,974,097, disclose means forcontinuously plating areas along the edges of a ice continuous strip. Itshould be noted, however, that the areas being electroplated arecontinuous areas running along the entire length of the strip, not aplurality of small areas on the faces of the strip. Thus, the problemsof solution distribution and isolation are much simpler than thoseencountered by the instant inventors.

All electrodeposited metals have crystalline structures which manifestthemselves in the physical properties and appearance of the platedmetal. In order to achieve plated deposits of suitable properties, it isnecessary to control the current density at which the plating is carriedout. Excessive current densities will result in deposits of poorquality. However, current densities which are too low will result inexcessively long plating cycles and markedly reduce the production rateof the plating operations. A particular problem encountered inconstructing apparatus which is suitable for continuous and simultaneouselectroplating of a large number of selected areas is to assuremaintenance of a suitably concentrated cation concentration at each ofthe discrete areas being plated. Without a suitably high concentration,it would be impossible to obtain a high quality plating in a desirablyshort time.

In commercial work, preparation of surfaces for plating is often asimportant as the electroplating step itself. This is especially so inelectroplating surfaces for use in microcircuit components. Thus,special care should be exercised in the construction of apparatus toassure that the surfaces to be electroplated are processed with minimalcontact by machine parts or by an operators hands. This requirement hasincreased the difiiculty of providing suitable apparatus for theelectroplating of a large number of selected areas along a single, butextensive, substrate.

SUMMARY OF THE INVENTION Therefore, it is an object of the instantinvention to provide apparatus which can quickly and conveniently effectthe uniform electroplating of a large number of preselected, discrete,surface zones of a strip of substrate as it is advanced along aprocessing line.

Still another object of the invention is to provide apparatus havingcompact means for maintaining the desired concentration of, andagitation of, the electroplating solution.

A further object of the invention is to provide novel means to protectsome areas of such sheet from contact with electroplating solution as itis continuously advanced therethrough.

Another object of the invention is to provide a novel process forelectroplating pre-selected and isolated face zones on a strip ofsubstrate to be plated.

Other objects of the invention will be obvious to those skilled in theart on reading the application.

The above objects have been economically and conveniently achieved byconstruction of electroplating apparatus which provides for themaintenance of suitably high cation contents in the immediate vicinityof all of the isolated surfaces being electroplated.

More particularly, the above objects have been attained by constructionof such apparatus comprising a continuous sealing web held in sealingcontact with the strip to be electroplated and having cut-outs orapertures in the web. The apertures define the areas of the strip whichare to be electroplated. Synchronizing means are provided to advance thestrip and sealing web in the desired register. This advance is mostadvantageously achieved in a seal box which holds the web in biasedcontact with the strip being electroplated and also provides means todistribute the flow of electrolyte solution.

The high cation contents are maintained, even while plating from anacid-gold solution at current densities of 15 to 25 amps per square footand above, by providing such a high flow of fluid proximate the surfacesbeing plated that excellent agitation is achieved. The ability to usethe apparatus at such high current densities markedly increases the linespeed which is possible, while still obtaining platings of good quality.

ILLUSTRATIVE EXAMPLE OF THE INVENTION In this application andaccompanying drawings are shown and described a preferred embodiment ofthe invention. Various alternatives and modifications thereof, aresuggested, but it is to be understood that these are not intended to beexhaustive and that other changes and modifications can be made withinthe scope of the invention. The suggestions herein are selected andincluded for purposes of illustration in order that others skilled inthe art will more fully understand the invention and the principlesthereof, and will be able to modify it and embody it in a variety offorms, each as may be best suited in the condition of a particular case.

In the drawings:

FIG. 1 is a schematic diagram illustrating the use of the apparatus ofthe invention.

FIG. 2 is a plan view of a part of the seal box in which the sheet to beelectroplated is carried through the electroplating bath.

FIG. 3, as is indicated by line 33 of FIG. 2, is a section of theapparatus shown in FIG. 2 showing the position of the metal sheetcarried through.

FIG. 4, as indicated by line 4--4 of FIG. 2, is a section of theapparatus shown in FIG. 2 showing a sheetbiasing means.

FIG. 5, as indicated by line 55 of FIG. 2 is a section of the apparatusshown in FIG. 2 showing the electrolyte-solution access path.

FIG. 6, as indicated by line 6-6 of FIG. 2, is also a section of theapparatus shown in FIG. 2 and shows electrolyte access paths.

FIG. 7 illustrates an exploded sandwich of a strip between sealing websand shows some detail of the foamed strips which selectively seal themetal substrate surface during its passage through the apparatus.

FIG. 8 shows some detail of the compressive edge seal achieved by thefoam strips.

FIG. 9 shows a plan view of the foamed strip.

FIG. 10 shows a plan view of a metallic strip of the type to beselectively electroplated.

Referring to FIG. 1, it is seen that a tank 10 is used to maintainelectrolytic solution 14 at a level 12 suflicient to cover silver anodes16. An upper sealing web 18 and a lower sealing web 19, each in the formof a flexible and compressible belt, are carried over indexing rolls 20and idler rolls 22. These sealing webs form a protective covering formetal strip 24 as it enters solution 14 and seal box 26. The sandwich 17formed by web 18, metal strip 24 and web 19 is carried through seal box26 under a compressive biasing force, as will be described more fullybelow. When the sandwich emerges from seal box 26 and solution 14, thesealing webs are pulled away from the metal strip and carried backaround indexing rolls 20. The metallic strip 24, having beenelectroplated, is carried off over a cathode contact roll 28 to furtherprocessing or packaging procedures. Cathode contact rolls 28 arepositioned at each end of the bath and are in electrical contact withmetal strip 24 so that strip 24 acts as the actual cathode in theselective electroplating operation.

Each cathode contact roll 28 and indexing roll 20 is driven from acommon motor by drive means which is conventional, forms no novel partof the invention, and is not shown in the drawings. The use of a commondrive source helps obtain what will be shown to be a necessarysynchronism between the advancement of metal strip 24 and sealing Webs18 and 19. This synchronization is further aided by positive-driveadvancing means in the form of teeth 30 on indexing rolls 20 and teeth32 on cathode contact rolls 28. These teeth, as will be seen below, fitcertain apertures or cut-outs in the strip or Web that they engage. Thusthey provide a means for achieving a positive advancement of the stripand Webs. Such a positive advancement helps to avoid slippage andcontributes to attaining the required synchronous advance of the strip24 and the webs 18 and 19 within which strip 24 is carried through sealbox 26.

Seal Box 26, in addition to acting as a seal means, 18 a flowdistributing means whereby flow is directed into agitated flow pathsproximate metal strip 24. Electrolytic solution is stored in reservoir34 and pumped therefrom, into a manifold box 36 from which it isdistributed via hoses 38 to distributing pipes 40 (see FIGS. 2, 3, and6) entering seal box 26. The solution then flows out into tank 10 and isre-circulated to reservoir 34 via pump 37 and conduit 39.

FIGS. 2 through 5 illustrate the configuration of the seal box 26through which the metal strip 24 and sealing webs 18 and 19 are carried.FIG. 2 shows the top cover plate 42. It has a series of elongated slots43 for egress of electrolytic solution from the apparatus after it hasbeen forced below cover plate 42 through distributing pipes 40. Atspaced intervals along cover plate 42 are screws 44. Along cover plate42 and between screws 44 are positioned springs 46.

FIG. 4, showing a section of the sealing box 26, illustrates how springs46 fit into an enlarged section of a channel 48 within a seal bar 50 tobias the bottom face 52 of seal bar 50 against upper sealing web 18.This biasing action causes sufficient compression of the compressiblesealing webs to seal the web-contacted surfaces of the metal strip fromcontact with plating solution. Seal bar 50 is slideably mounted withinseal housing 54. Screws 44 are used to fasten cover 42 into housing 54,and thereby provide means to compress spring 46 to the desired 'biasinglevel.

Referring to FIGS. 2, 3, and 5, it is seen that bottom face 52 of biasedseal bar 50 also is cut out to provide elongated apertures 51 for theelectrolytic solution to reach the sandwich formed by sealing webs 18and 19 and metal strip 24. Apertures 51 are in the general shape of theelongated slots 43 and are positioned below elongated slots 43.

Were the device being illustrated to be adapted for plating both sidesof a workpiece, bridge 58 which forms a web-supporting surface in sealhousing 54 would also have a series of elongated slots therein and lowersealing web would have apertures corresponding to apertures 60 in uppersealing web 18.

In the embodiment of the invention being described electrolytic solutionis pumped into seal box 26 through distributing pipes 40 at a highvelocity. The velocity is sufiicient to cause a great deal of turbulencein channel 48 and this turbulence liquid is also carried throughapertures 60, in upper sealing web 18, to contact only those areas 62 ofmetal strip 24 which are exposed by apertures 60. Flow paths of theelectrolytic solution are generally shown on FIG. 3.

FIGS. 9 and 10 show plan views of the upper sealing web 18 and strip 24.Apertures 60 in web 18 define the passage through which agitated liquidfrom channel 48 reaches strip 24. When these apertures are biasedagainst strip 24, and when they do not move in relation to the strip,but are synchronized to move along with it, the areas 62 on the stripwill be selectively electroplated whereas other areas of strip 24 willnot be electroplated. In the illustrated embodiment of the invention theaperture-free bottom sealing web provides means to seal bottom surfaceof strip 24 against contact with electrolytic solution.

FIGS. 7 and 8 show details of the construction of the sealing webs 18and 19. These webs consist of a laminated structure having a neoprenefoam layer 62, a nylontextile reinforcing fabric 64 and a protective andlubricative cover layer 66 formed of a poly (tetrafluoroethylene)polymer such as that sold under the trade designation Teflon by E. I. duPont de Nemours and Company, Inc. In FIG. 8, it is seen that neoprenefoam compresses under moderate pressure to form a protective liquid sealalong edges 68 of strip 24. Cover layer 66 material aids in the ease ofpassage of the sandwich 17 through seal box 26 because of its loWcoeflicient of friction.

The required synchronized advance of sheet 24 and apertures sealing web18 is facilitated by the engagement of teeth 32 on cathode contact rolls28 with the slots 70 along the sides of sheet 24 and the engagement ofteeth 30 on indexing rolls with the apertures. Teeth 32 and are advancedthe same circumferential distance per unit time and this assures that,once the apertures 60 in web 18 and the areas 62 in strip 24 have beenbrought into desired registration with one another, the relativerotation of rolls 28 and 20 will maintain that registration.

While the instant invention has been described with respect toelectroplating processes, it will be realized that it also can be usedin etching processes. Etching is the reverse of electroplating withmetal being removed from, rather than added to, the strip beingprocessed. Similar problems are encountered in each process. Forexample, it is necessary to obtain good agitation of electroplatingsolution to maintain a high concentration of cation next to the stripbeing electroplated, such agitation is required during etching tomaintain a suitably low concentration of cation next to the strip beingetched.

it is also to be understood that the following claims are intended tocover all of the generic and specific features of the invention hereindescribed, and all statements of the scope of the invention which, as amatter of language, might be said to fall therebetween.

What is claimed is:

1. Electroplating apparatus suitable for selectively electroplatingdiscrete areas of a strip, said apparatus comprising:

(a) a sealing means comprising a continuous sealing web, in sealingcontact with said strip and having apertures therein defining the areasto be electroplated;

(b) means to synchronously advance said apertures and said substrate andmaintain said discrete areas and said apertures in register with eachother;

(e) cathode contact means allowing said substrate to actd as a cathodeduring said synchronous advance; an

(d) means to direct agitated electroplating solution into said aperturesas they advance, and wherein said means to synchronously advance saidapertures and said strip comprise:

(1) a cathode contact roll comprising means to engage and advance saidmetal strip, and

(2) an indexing roll comprising teeth for engaging said apertures.

2. Apparatus as defined in claim 1 adapted for plating discrete areas ontwo sides of a foraminous sheet, where- 1n said sealing means is formedof two webs, each comprising a compressible polymeric foam with the websoverlapping the lateral edges of said strip to be electroplated and, oncompression, forming means to protect such edges from contact with saidelectroplating solution, wherein opposed apertures of said two webs arein register forming a common conduit for said solution.

3. Electroplating apparatus suitable for selectively electroplatingdiscrete areas of a strip, said apparatus comprising:

(a) a sealing means comprising a continuous sealing web, in sealingcontact with said strip and having apertures therein defining the areasto be electroplated;

(b) means to synchronously advance said apertures and said substrate andmaintain said discrete areas and said apertures in register with eachother;

(e) cathode contact means allowing said substrate to act as a cathodeduring said synchronous advance; and

(d) means to direct agitated electroplating solution into said aperturesas they advance, and wherein said sealing means comprises an elongateseal box comprising:

(1) means to support said sealing web and sald strip to beelectroplated, and

(2) an elongate seal bar forming means to press said web and stripagainst said support means, said seal bar comprising apertures formingmeans for passage of electrolyte solution.

4. Apparatus as defined in claim 3, wherein said seal bar comprises achannel therein, said channel forming means to position and hold springswhich are biased between the bottom of said channel and a housing towhich said seal bar is attached.

5. Apparatus as defined in claim 3, wherein said sealing means comprisesbiasing means bearing against said seal bar and a housing in which saidseal bar is retained.

6. Apparatus as defined in claim 5, wherein said housing comprises meansto adjust the degree of biasing pressure on said seal bar.

7. Electroplating apparatus suitable for selectively electroplatingdiscrete areas of a strip, said apparatus comprising:

(a) a sealing means comprising a continuous sealing web, in sealingcontact with said strip and having apertures therein defining the areasto be electroplated;

(b) means to synchronously advance said apertures and said substrate andmaintain said discrete areas and said apertures in register with eachother;

(0) cathode contact means allowing said substrate to act as a cathodeduring said synchronous advance; and

(d) means to direct agitated electroplating solution into said aperturesas they advance;

wherein said apparatus is adapted for plating discrete areas on twosides of a foraminous sheet, wherein said sealing means is formed of twowebs, each comprising a compressible polymeric foam with the websoverlapping the lateral edges of said strip to be electroplated and, oncompression, said webs forming means to protect such edges from contactwith said electroplating solution and wherein opposed apertures of saidtwo webs are in register forming a common conduit for said solution; andwherein said sealing means comprises an elongate seal box comprising:

(1) means to support said sealing webs and strip to be electroplated;and

(2) an elongate seal bar pressing said webs and strip against saidsupport means, said seal bar comprising apertures forming means forpassage of electrolyte solution.

8. Electroplating apparatus suitable for selectively electroplatingdiscrete areas of a strip, said apparatus comprising:

(a) a sealing means comprising a continuous sealing web, in sealingcontact with said strip and having apertures therein defining the areasto be electroplated;

=(b) means to synchronously advance said apertures and said substrateand maintain said discrete areas and said apertures in register witheach other;

(c) cathode contact means allowing said substrate to act as a cathodeduring said synchronous advance; and

(d) means to direct agitated electroplating solution into said aperturesas they advance, and wherein said sealing means comprises an elongateseal box comprising:

( 1) means to support said sealing web and strip to be electroplated,and

(2) an elongate seal bar pressing said web and strip against saidsupport means, said seal bar comprising apertures forming means forpassage of electrolyte solution.

9. Apparatus as defined in claim 8, wherein said seal bar comprises achannel therein, said channel forming means to position and hold springswhich are biased between the bottom of said channel and a housing towhich said seal bar is attached.

10. Electroplating apparatus Suitable for selectively electroplatingdiscrete areas of a strip, said apparatus comprising:

(a) a sealing means comprising a continuous sealing web, in sealingcontact with said strip and having apertures therein defining the areasto be electro plated;

(b) means to synchronously advance said apertures and said substrate andmaintain said discrete areas and said apertures in register with eachother;

(e) cathode contact means allowing said substrate to act as a cathodeduring said synchronous advance; and

(d) means to direct agitated electroplating solution into said aperturesas they advance,

and said apparatus being adapted for plating discrete areas on two sidesof a foraminous sheet, wherein said sealing means is formed of two webs,overlapping the lateral edges of said strip to be electroplated and, oncompression, forming means to protect such edges from contact with saidelectroplating solution and wherein opposed apertures of said two websare in register forming a common conduit for said solution.

11. Apparatus as defined in claim 10, wherein said sealing means ispositioned in a bath of re-circulating electroplating solution.

12.. Apparatus as defined in claim 8, comprising two said sealing webs,one adapted to contact each side of said strip during passage throughelectrolyte solution;

a chamber for holding electrolyte solution and means to recirculate saidsolution through said chamber;

a seal box mounted in said chamber and comprising support means for saidwebs and said strip, and

a biasing means to bias said webs and said strip against said supportmeans.

13. Apparatus as defined in claim 8, wherein said sealing meanscomprises biasing means bearing against said seal bar and a housing inwhich said seal bar is retained.

14. iElectroplating apparatus suitable for selectively electroplatingdiscrete areas of a strip, said apparatus comprising:

'(a) a sealing means comprising a continuous sealing web, in sealingcontact with said strip and having apertures therein defining the areasto be electroplated;

(b) means to synchronously advance said apertures and said substratethrough an electroplating zone and maintain said discrete areas and saidapertures in register with each other;

(c) cathode contact means allowing said substrate to act as a cathodeduring said synchronous advance; and

(d) a plurality of discharge means arranged serially along saidelectroplating zone to direct agitated electroplating solution into saidapertures and against said discrete areas as they advance through saidzone.

15. Apparatus as defined in claim 14 wherein said sealing meanscomprises a compressible belt of polymeric foam and means forcompressing said belt against said substrate to be electroplated.

References Cited UNITED STATES PATENTS 3,483,113 12/ 1969 Carter 2042063,539,490 11/1970 Gannoe 2.04-224 X 3,274,092 9/1966 Marantz 204 2243,644,181 2/ 1972 Donaldson 204224 X FOREIGN PATENTS 1,098,182 1/ 1968Great Britain 204-15 JOHN H. MACK, Primary Examiner D. R. VALENTINE,Assistant Examiner Us. 01. X.R. 2o4 224 R, 225, 237, 27s

